Modular humeral head

ABSTRACT

A modular humeral head system includes a housing having an outer surface and an inner surface. A hemispherical socket formed on one end of the inner surface and threads formed on the other end of the inner surface. A cap is attached at the threaded end of the housing. The cap has one or more threaded holes that run from the top surface to bottom surface of the cap. A screw may be inserted in each hole. The modular humeral head system also includes an intermediate piece having a hemispherical head at one end of a tapered shaft. The tapered shaft is inserted in a humeral stem. The hemispherical head and the hemispherical socket form a ball and socket coupling. A trial head may be impacted on the housing. The trial head has one or more holes that are aligned with the screws inserted in the cap. 
     In use, the assembly of the trial head, cap and housing can be adjusted to be in any angular orientation about hemispherical head. The tightening of the one or more screws fixes the angular position of the trial head. An optimum position for the trial head is established via trial reduction, the one or more screws tightened to fix the position of the head and the trial head is replaced with a humeral head of corresponding size and shape. The maximum adjustment of the angular position may be limited by a limiting mechanism. In another embodiment, bone cement or other bio-compatible material is introduced in a chamber formed between the cap and the hemispherical head.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.11/599,602, filed Nov. 13, 2006, the entire disclosure of which ishereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present disclosure relates to a prosthetic device system forrepairing ball-and-socket type joints in a human body. More particularlythe disclosure relates to a modular anatomic adjustable prostheticdevice system for the shoulder and hip joints.

2. Description of Prior Art

A joint replacement procedure is sometimes necessary to repair a jointhaving a diseased or damaged articulating surface. Such a procedureinvolves removal of the diseased or damaged portions of the joint andreplacing them with a prosthetic implant. This is often a desirableprocedure for ball-and-socket type joints, particularly the shoulder andhip joints. A shoulder joint replacement procedure, for example, ofteninvolves removal of the humeral head and replacement thereof with animplant including a stem and a head. It is important that the implant bepositioned correctly within the joint in order to ensure thatappropriate joint kinematics, including range of motion, are preservedso as to replicate, as closely as possible, those of the original joint.

The classical prosthetic humeral component is known as the NEER-type andis a one-piece component which is available in many different sizes forreplacement of the upper portion of the humerus. The classical humeralcomponent has a stem which is designed to extend downwardly into acavity formed within the humerus and which is secured with cement orwith coatings which promote bone ingrowth to secure the stem. The stemis provided with a generally hemispherical head portion which isconfigured to replace the head of the organic humerus. However, theorientation of the humeral head relative to the stem varies from patientto patient. Therefore, it is desirable that the orientation of thehumeral head be adjustable.

One adjustable device is described in U.S. Pat. No. 5,741,335 to Gerberet al. The shoulder prosthesis of Gerber et al. includes a humeral stemdesigned to be implanted within the patient's humeral canal and a headportion designed to cooperate with the glenoid cavity of a shoulder. Thehead portion has a spherical shape generated by revolution about anaxis. A spherical socket is formed in the head portion for housing aball that is fixed to a proximal end of the stem. The axis of revolutionof the head portion is off-set with respect to the center of the ball.The assembly formed by the socket and the ball constitutes a jointcapable of making the orientation of the head portion vary in relationto the stem by rotation about the center of the ball. The head portionis locked to the stem by a conical push rod which moves into an axialconical bore under the action of a tightening screw. The push rod causescompression of the ball against the spherical cavity by blocked lateralexpansion of the ball thereby locking the head portion on the stem.

However, there is a need for prosthetic device system that allow quickand precise adjustment of the position of the humeral head during trialreduction, and once an optimal placement of the humeral head isdetermined, positively locks the prosthesis in that position.

BRIEF SUMMARY OF THE INVENTION

The modular humeral head system of the present invention overcomes theshortcomings of the prior art. The modular humeral head system includesa housing having an outer surface and an inner surface. A hemisphericalsocket is formed on one end of the inner surface and threads formed onthe other end of the inner surface. The outer surface has a Morse taper.A cap is attached at the threaded end of the housing. The cap has threethreaded holes that run from the top surface to bottom surface of thecap. A screw may be inserted in each hole. The head of the screw isformed to allow engagement with a screw driver. The modular humeral headsystem also includes an intermediate piece having a hemispherical headat one end of a tapered shaft. The tapered shaft has Morse taper thatmatches a female taper in a humeral stem. Humeral stem may come indifferent size. A top surface of the hemispherical head has three flatsurfaces. These flat surfaces are facing the holes in the cap such thatif the screws are advanced in the holes, each screw will contact oneflat surface. The hemispherical head and the hemispherical socket form aball and socket coupling. A trial head may be impacted on the housing.The trial head has three holes that are aligned with the three screwsinserted in the cap. These holes provide access to the screws withoutremoving the trial head from the housing.

In use, the assembly of the trial head, cap and housing can be adjustedto be in any angular orientation about hemispherical head. Next, thetapered shaft of the intermediate piece is inserted in the humeral stemto create a modular humeral head assembly for trial reduction of theshoulder joint. The humeral stem is inserted in the prepared medullarycanal of humeral bone. With the modular humeral head assembly installedin the medullary canal, the shoulder joint is reduced. The reduced jointis evaluated for being optimal. If any adjustment in the angularlocation of the trial head is needed, the screws are accessed throughholes in the trial head and loosened. Once the screws are loosened, theangular position of the trial head is adjusted and then the screws aretightened. The tightening of the screws fixes the angular position ofthe trial head. The shoulder joint is evaluated again with the changedposition of the trial head, and the process repeated if necessary. Oncean optimum position for the trial head is established, the trial head isreplaced with a humeral head of corresponding size and shape.

A second embodiment of the modular humeral head system is similar to theabove described embodiments in many aspects except that the cap in thesecond embodiment has one hole. A screw may be inserted in the hole. Themodular humeral head system of the second embodiment also includes anintermediate piece having a hemispherical head at one end of a taperedshaft. A top surface of the hemispherical head has a shaped surface. Theshaped surface is facing the hole such that if the screw is advanced inthe hole, it will contact the shaped surface. The shaped surface and tipof the screw have complimentary shapes. The complimentary surfaces onthe tip of screw and the shaped surface allow them to mate in a stablemanner. A trial head may be impacted on the housing of the secondembodiment. The trial head has one hole that is aligned with the screwinserted in the cap. This hole provides access to the screw withoutremoving the trial head from the housing. The optimum position for theprosthesis is determined in a manner similar to one described inconnection with the first embodiment. One difference is that in thesecond embodiment there is only one screw instead of the three screws inthe first embodiment. Once an optimum position for the trial head isestablished, the trial head is removed. With the trial head removed,bone cement or other bio-compatible material is introduced in a chamberformed between the cap and the hemispherical head. The Bone cement orother bio-compatible material cures in the chamber and turns to a hardmass. The presence of this hard mass in the chamber prevents the housingfrom moving relative to the hemispherical head. The hardening of thebone cement or other bio-compatible material in small cavities formed onthe lower surface of the cap and the facing surface of the hemisphericalhead prevents axial rotation of the hemispherical head within thehousing. A humeral head of size and shape corresponding to the trialhead is impacted on the housing after the bone cement or otherbio-compatible material has hardened.

A third preferred embodiment of modular humeral head assembly is similarto the first embodiments in various aspects. This embodiment has ahousing shaped generally like a hollow cylinder. Housing has an innersurface that takes the form of a stepped cylinder having four differentdiameters. The central longitudinal axis of the inner surface and thecentral longitudinal axis of the outer surface are parallel to eachother and offset from each other by a fixed distance. A cap isinsertable in housing and has three holes that run from top surface tobottom surface. A screw may be inserted in each hole. A cylindrical postprojects from the bottom of cap. The assembly includes an intermediatepiece having a hemispherical head at one end of a tapered shaft. A topsurface of the hemispherical head has three hemi-cylindrical cutouts.Hemi-cylindrical cutouts are facing holes such that if screws areadvanced in holes, each screw will contact one hemi-cylindrical cutout.Intermediate piece has a blind hole in its center. Hole is shaped toallow insertion of the cylindrical post. The cylindrical post is loosein hole, thereby allowing limited relative motion between cap andintermediate piece. The assembly also includes a spherical seat ring.Spherical seat ring has an inner spherical surface that mates withspherical surface of hemispherical head to form a joint that allowsrotational movement between intermediate piece and spherical seat ring.Spherical seat ring has an outer surface that is sized to mate with thecylindrical surfaces on the inside of housing. Trial head may be usedwith the present embodiment in same manner as discussed previously. Theoptimum position for the prosthesis is determined in a manner similar toone described in connection with the first embodiment.

The modular humeral head systems described above may be made availableas a kit. The kit would contain a set of trial heads and a correspondingset of humeral heads. The kit may also contain humeral stems of varioussizes.

Additional objects and advantages of the invention will become apparentto those skilled in the art upon reference to the detailed descriptiontaken in conjunction with the provided figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of an assembly of housing and anintermediate piece of the first embodiment of a modular humeralprosthesis.

FIG. 2 is an isometric view of a cap for the first embodiment of amodular humeral prosthesis.

FIG. 3 is an isometric view of three screws for the first embodiment ofa modular humeral prosthesis.

FIG. 4 is a sectional view of a humeral stem for the first embodiment ofa modular humeral prosthesis.

FIG. 5 is a sectional isometric view of a humeral head for the firstembodiment of a modular humeral prosthesis.

FIG. 6 is an isometric view of a trial head for the first embodiment ofa modular humeral prosthesis.

FIG. 7 is an isometric view of an assembly of the housing, intermediatepiece, cap and humeral stem for the first embodiment of a modularhumeral prosthesis.

FIG. 8 is an isometric view of an assembly of housing and anintermediate piece of the second embodiment of a modular humeralprosthesis.

FIG. 9 is an isometric view of a cap for the second embodiment of amodular humeral prosthesis.

FIG. 10 is an isometric view of the screw for the second embodiment of amodular humeral prosthesis.

FIG. 11 is a sectional view of a humeral stem for the second embodimentof a modular humeral prosthesis.

FIG. 12 is a sectional isometric view of a humeral head for the secondembodiment of a modular humeral prosthesis.

FIG. 13 is an isometric view showing the intermediate piece, cap and aportion of the humeral head for the second embodiment of a modularhumeral prosthesis.

FIG. 14 is an isometric view of a trial head for the second embodimentof a modular humeral prosthesis.

FIG. 15 is an isometric view of an assembly of the housing, intermediatepiece, cap and humeral stem for the second embodiment of a modularhumeral prosthesis.

FIG. 16 is a cross sectional view of an assembly of the intermediatepiece, housing, cap and a screw of the second embodiment of a modularhumeral prosthesis.

FIG. 17 is a view of an assembly of a housing, an intermediate piece, aseat ring, a cap and screws of the third embodiment of a modular humeralprosthesis.

FIG. 18 is an isometric view of the housing shown in FIG. 17.

FIG. 19 is an isometric view of the cap shown in FIG. 17.

FIG. 20 is another isometric view of the cap of FIG. 17 showing the topsurface of the cap.

FIG. 21 is an isometric view of the intermediate piece shown in FIG. 17.

FIG. 22 is an isometric view of the spherical seat ring shown in FIG.17.

FIG. 23 is a cross sectional view of an assembly of a housing, anintermediate piece, a seat ring, a cap and screws of the thirdembodiment of a modular humeral prosthesis.

FIG. 24 shows a modular prosthesis kit of the first, second or thirdembodiment.

DETAILED DESCRIPTION

FIGS. 1-5 show various parts of a first embodiment of a modular humeralhead assembly. FIG. 1 shows a housing 100. Housing 100 is shapedgenerally like a hollow cylinder. Housing 100 has an outer surface 102and an inner surface 104. A hemispherical socket 106 is formed on oneend of inner surface 104. Threads 108 are formed on the other end ofinner surface 104. Outer surface 102 has a Morse taper.

A cap 110 (FIG. 2) is attached at the threaded end of housing 100. Cap110 has a generally cylindrical structure. The outside cylindricalsurface 112 of cap 110 has threads 114. Threads 114 mate with threads108 formed on inner surface 104. Cap 110 has a top surface 116 and abottom surface 118. Top surface 116 and bottom surface 118 may besubstantially parallel to each other and orthogonal to cylindricalsurface 112. Cap 110 has three holes 120 that run from top surface 116to bottom surface 118. Holes 120 have internal threads 122 formed ontheir periphery. A screw 124 (FIG. 3) may be inserted in each hole 120.The head of screw 124 is formed to allow engagement with a screw driver,for example, a hexagonal screw driver 140 (FIG. 6).

An intermediate piece 126 (FIG. 1) has a hemispherical head 128 at oneend of a tapered shaft 129. Tapered shaft 129 has a Morse taper thatmatches a female taper 130 in a humeral stem 132 (FIG. 4). Humeral stem132 may come in different size, each stem being capable of assembly withtapered shaft 129. A top surface 134 of hemispherical head 128 has threeflat surfaces 136. Flat surfaces 136 may form an angle with thelongitudinal axis of intermediate piece 126, for example, flat surface136 may form an eight (8) degree angle with the longitudinal axis ofintermediate piece 126. Flat surfaces 136 are facing holes 120 such thatif screws 124 are advanced in holes 120, each screw 124 will contact oneflat surface 136. FIG. 7 shows an assembly of intermediate piece 126,housing 100, cap 110 and humeral stem 132. Intermediate piece 126,housing 100, cap 110 and screws 124 may be factory assembled.

FIG. 6 shows a trial head 138. Trial head 138 comes in different sizesand hemispherical heights. Trial head 138 may have a hollowhemispherical shape. The inside surface of trial head 138 has a Morsetaper that matches the male taper on outer surface 102 of housing 100.Trial head 138 has three holes 142 that are aligned with three screws124 inserted in cap 110. Holes 142 provide access to screws 124 withoutremoving trial head 138 from housing 100.

In use, cap 110 is screwed in housing 100 which in turn is attached tohemispherical head 128 via a ball-and-socket type coupling. In theassembled state, cap 110 and housing 100 are movably attached tohemispherical head 128 such that they can rotate about the hemisphericalhead, thereby allowing angular adjustment. The humeral bone is exposedand prepared by known surgical methods. Humeral stem 132 is inserted inthe prepared medullary canal of humeral bone. Next, trial head 138 isassembled on housing 100. The matching Morse taper on housing 100 andtrial head 138 fixes trial head 138 to housing 100. The assembly oftrial head 138, cap 110 and housing 100 can be adjusted to be in anyangular orientation about hemispherical head 128. Next, tapered shaft129 of intermediate piece 126 is inserted in humeral stem 132 to createa modular humeral head assembly for trial reduction of the shoulderjoint. With the modular humeral head assembly installed in the medullarycanal, the shoulder joint is reduced. The reduced joint is evaluated forbeing optimal. For example, the reduced joint is evaluated for havingproper muscle tension and retroversion angle. If any adjustment in theangular location of trial head 138 is needed, one or more of screws 124are accessed through holes 142 in trial head 138 and loosened usingscrew driver 140. Once the desired number of screws 124 are loosened,the angular position of trial head 138 is adjusted and then screws 124are tightened. The tightening of screws 124 fixes the angular positionof trial head 138. The shoulder joint is evaluated again with thechanged position of trial head 138, and the process repeated ifnecessary. Once an optimum position for trial head 138 is established,trial head 138 is replaced with a humeral head 144 (FIG. 5) ofcorresponding size and shape.

Humeral head 144 comes in different sizes and hemispherical heights.Humeral head 144 may have a hollow hemispherical shape. An insidesurface 146 of Humeral head 144 has a Morse taper that matches maletaper on outer surface 102 of housing 100.

The modular humeral head system may be made available as a kit (see FIG.24). The kit would contain a set of trial heads 138 and a correspondingset of humeral head 144. The kit may also contain humeral stems 132 ofvarious sizes. Each humeral stem 132 may be made such that it can beassembled with tapered shaft 129 of intermediate piece 126. The housingassembly 350 shown in FIG. 24, in one embodiment, includes intermediatepiece 129, housing 100, cap 110 and screws 124 assembled at the factory.

FIGS. 8-12 show various parts of a second embodiment of modular humeralhead assembly. FIG. 8 shows a housing 200. Housing 200 is shapedgenerally like a hollow cylinder. Housing 200 has an outer surface 202having a Morse taper, and an inner surface 204. A hemispherical socket206 is formed on one end of inner surface 204. Threads 208 are formed onthe other end of inner surface 204. The construction of housing 200 issimilar to construction of housing 100 discussed previously.

A cap 210 (FIG. 9) is attached at the threaded end of housing 200. Cap210 has a generally cylindrical structure. The outside cylindricalsurface 212 of cap 210 has threads 214. Threads 214 mate with threads208 formed on inner surface 204. Cap 210 has a top surface 216 and abottom surface 218. Top surface 216 and bottom surface 218 may besubstantially parallel to each other and orthogonal to cylindricalsurface 212. Cap 210 has a hole 220 that runs from top surface 216 tobottom surface 218. Hole 220 has internal threads 222 formed on itsperiphery. A screw 224 (FIG. 10) may be inserted in hole 220. The headof screw 224 is formed to allow engagement with a screw driver, forexample, a hexagonal screw driver 240 (FIG. 14).

An intermediate piece 226 (FIG. 8) has a hemispherical head 228 at oneend of a tapered shaft 229. Tapered shaft 229 has a Morse taper thatmatches a female taper 230 in a humeral stem 232 (FIG. 11). Humeral stem232 may come in different sizes, each stem being capable of assemblywith tapered shaft 229. A top surface 234 of hemispherical head 228 hasa shaped surface 236. Shaped surfaces 236 is facing hole 220 such thatif screw 224 is advanced in hole 220, it will contact shaped surface236. Shaped surface 236 and tip of screw 224 have complimentary shapes,for example, shaped surface 236 may be convex and the tip of screw 224may be concave or vice versa (see FIG. 16). The complimentary surfaceson tip of screw 224 and shaped surface 236 allow them to mate in astable manner. Since screw 224 is rigidly connected to cap 210, which inturn is rigidly connected to housing 200, tightening of screw 224against shaped surface 236 results in fixing housing 200 relative tohemispherical head 228. However, since the contact surface between screw224 and shaped surface 236 is not large it may be desirable to furtherstabilize the relative positioning of housing 200 relative tohemispherical head 228. FIG. 15 shows an assembly of intermediate piece226, housing 200, cap 210 and humeral stem 232. Intermediate piece 226,housing 200, cap 210 and screw 224 may be factory assembled.

FIG. 14 shows a trial head 238. Trial head 238 comes in different sizesand hemispherical heights. Trial head 238 may have a hollowhemispherical shape. The inside surface of trial head 238 has a Morsetaper that matches the male taper on outer surface 202 of housing 200.Trial head 238 has a hole 242 that is aligned with screw 224 inserted incap 210. Hole 242 provides access to screw 224 without removing trialhead 238 from housing 200.

In use, cap 210 is screwed in housing 200 which in turn is attached tohemispherical head 228 via a ball-and-socket type coupling. In theassembled state, cap 210 and housing 200 are movably attached tohemispherical head 228 such that they can rotate about the hemisphericalhead 228, thereby allowing angular adjustment. The humeral bone isexposed and prepared by known surgical methods. Humeral stem 232 isinserted in the prepared medullary canal of humeral bone. Next, trialhead 238 is assembled on housing 200. The matching Morse taper onhousing 200 and trial head 238 fixes trial head 238 to housing 200. Theassembly of trial head 238, cap 210 and housing 200 can be adjusted tobe in any angular orientation about hemispherical head 228. Next,tapered shaft 229 of intermediate piece 226 is inserted in humeral stem232 to create a modular humeral head assembly for trial reduction of theshoulder joint. With the modular humeral head assembly installed in themedullary canal, the shoulder joint is reduced. The reduced joint isevaluated for being optimal. For example, the reduced joint is evaluatedfor having proper muscle tension and retroversion angle. If anyadjustment in the angular location of trial head 238 is needed, screw224 is accessed through hole 242 in trial head 238 and loosened usingscrew driver 240. Once screw 224 is loosened, the angular position oftrial head 238 is adjusted and then screw 224 is tightened. Thetightening of screw 224 fixes the angular position of trial head 238.The shoulder joint is evaluated again with the changed position of trialhead 238, and the process repeated if necessary. Once an optimumposition for trial head 238 is established, trial head 238 is removed.

With trial head 238 removed, bone cement or other bio-compatiblehardenable material is introduced in chamber 239 via an aperture 225.Screw 224 has aperture 225 that is in fluid communication with a chamber239 enclosed by intermediate piece 226, housing 200 and cap 210. Thebone cement or other bio-compatible material is introduced in chamber239 under pressure. Cap 210 has one or more air bleeding holes 248 thatallow air to escape from chamber 239 when pressurized bone cement orother bio-compatible material is introduced in chamber 239. The bonecement or other bio-compatible material cures in chamber 239 and turnsto a hard mass. The presence of this hard mass in chamber 239 preventshousing 200 from moving relative to hemispherical head 228. Cap 210 hasone or more small cavities 250 formed on bottom surface 218.Hemispherical head 228 also has small cavities 252 formed on itssurface. Small cavities 250 and 252 are located in chamber 239. The bonecement or other bio-compatible material enters small cavities 250 and252 and hardens therein upon curing. The hardening of the bone cement orother bio-compatible material in small cavities 250 and 252 preventsaxial rotation of hemispherical head within housing 200. A humeral head244 of size and shape corresponding to trial head 238 is impacted onhousing 200 after the bone cement or other bio-compatible material hashardened.

Humeral head 244 comes in different sizes and hemispherical heights.Humeral head 244 may have a hollow hemispherical shape. The insidesurface 246 of Humeral head 244 has a Morse taper that matches maletaper on outer surface 202 of housing 200.

The modular humeral head system described above may be made available asa kit (see FIG. 24). The kit would contain a set of trial heads 238 anda corresponding set of humeral heads 244. The kit may also containhumeral stems 232 of various sizes. Each humeral stem 232 may be madesuch that it can be assembled with tapered shaft 229 of intermediatepiece 226. The housing assembly 350 shown in FIG. 24, in one embodiment,includes intermediate piece 226, housing 200, cap 210 and screw 224assembled at the factory.

FIG. 17 shows various parts of a third preferred embodiment of modularhumeral head assembly. FIGS. 17 and 18 show a housing 300. Housing 300is shaped generally like a hollow cylinder. Housing 300 has an outersurface 302 and an inner surface 304. Inner surface 304 takes the formof a stepped cylinder having four different diameters. Housing 300 alsohas a top surface 306 and a bottom surface 308. Top surface 306 has anopening 310 and bottom surface 308 has an opening 312. Opening 310,opening 312, are coaxial. The central longitudinal axis of opening 310and opening 312 and the central longitudinal axis of the outer surface302 are parallel to each other and off set from each other by a fixeddistance, for example 2 millimeter. Outer surface 302 has a Morse taper.

A cap 314 (FIGS. 17, 19 and 20) is insertable in housing 300 throughopening 312. Cap 314 has a generally cylindrical structure. Outsidecylindrical surfaces 316 and 318 mate with the stepped cylindricalsurfaces on the inside of housing 300. A top surface 320 of cap 314projects out from opening 310 in housing 300. Cap 314 has a top surfaceand a bottom surface and three holes 322 that run from top surface tobottom surface. Holes 322 have internal threads formed on theirperiphery. A screw 324 may be inserted in each hole 322. The head ofscrew 324 is formed to allow engagement with a screw driver, forexample, a hexagonal screw driver 140 (FIG. 6). A cylindrical post 321projects from the bottom of cap 314. Post 321 may be of any suitableshape, for example, it may have a square or an oval cross section.

An intermediate piece 326 (FIGS. 17 and 21) has a hemispherical head 328at one end of a tapered shaft 329. Tapered shaft 329 has a Morse taperthat matches a female taper 130 in a humeral stem 132 (FIG. 4). Humeralstem 132 may come in different size, each stem being capable of assemblywith tapered shaft 329. A top surface 334 of hemispherical head 328 hasthree hemi-cylindrical cutouts 336. Hemi-cylindrical cutouts 336 arefacing holes 322 such that if screws 324 are advanced in holes 322, eachscrew 324 will contact one hemi-cylindrical cutout 336. Intermediatepiece 326 has a blind hole 333 in its center. Hole 333 is shaped toallow insertion of post 321. Post 321 is loose in hole 333, therebyallowing limited relative motion between cap 314 and intermediate piece326.

FIGS. 17 and 22 show a spherical seat ring 335. Spherical seat ring 335has an inner spherical surface 337 that mates with spherical surface ofhemispherical head 328 to form a joint that allows rotational movementbetween intermediate piece 326 and spherical seat ring 335. Sphericalseat ring 335 has an outer surface 339 that is sized to mate with thecylindrical surfaces on the inside of housing 300.

FIG. 6 shows a trial head 138. Trial head 138 may be used with thepresent embodiment in same manner as discussed previously.

FIG. 23 shows an assembly of intermediate piece 326, housing 300, screws324, cap 314 and spherical seat ring 335. Intermediate piece 326,housing 300, cap 314 and spherical seat ring 335 are factory assembled.To assemble, spherical seat ring 335 is passed over the stem of taperedshaft 329 to bring its inner spherical surface 337 in contact with thespherical surface of hemispherical head 328. Next, cap 314 is insertedin housing 300 which in turn is attached to spherical seat ring 335 vialaser welding. In the assembled state, cap 314 and housing 300 aremovably attached to hemispherical head 328 via spherical seat ring 335such that they can rotate about the hemispherical head 328, therebyallowing angular adjustment. However, post 321 touches the walls of hole333 when head 328 is moved beyond a certain limit, thereby acting as alimit stop on the movement of head 328. The humeral bone is exposed andprepared by known surgical methods. Humeral stem 132 is inserted in theprepared medullary canal of humeral bone. Next, trial head 138 isassembled on housing 300. The matching Morse taper on housing 300 andtrial head 138 fixes trial head 138 to housing 300. The assembly oftrial head 138, cap 314 and housing 300 can be adjusted to be in anyangular orientation about hemispherical head 328. Next, tapered shaft329 of intermediate piece 326 is inserted in humeral stem 132 to createa modular humeral head assembly for trial reduction of the shoulderjoint. With the modular humeral head assembly installed in the medullarycanal, the shoulder joint is reduced. The reduced joint is evaluated forbeing optimal. For example, the reduced joint is evaluated for havingproper muscle tension and retroversion angle. If any adjustment in theangular location of trial head 138 is needed, one or more of screws 324are accessed through holes 142 in trial head 138 and loosened usingscrew driver 140. Once the desired number of screws 324 are loosened,the angular position of trial head 138 is adjusted and then screws 324are tightened. The tightening of screws 324 fixes the angular positionof trial head 138. The shoulder joint is evaluated again with thechanged position of trial head 138, and the process repeated ifnecessary. Once an optimum position for trial head 138 is established,trial head 138 is replaced with a humeral head 144 (FIG. 5) ofcorresponding size and shape.

Humeral head 144 comes in different sizes and hemispherical heights.Humeral head 144 may have a hollow hemispherical shape. An insidesurface 146 of Humeral head 144 has a Morse taper that matches maletaper on outer surface 302 of housing 300. The housing assembly 350shown in FIG. 24, in one embodiment, includes intermediate piece 329,housing 300, cap 314, spherical seat ring 335 and screws 324 assembledat the factory.

The modular humeral head system may be made available as a kit (see FIG.24). The kit would contain a set of trial heads 138 and a correspondingset of humeral head 144. The kit may also contain humeral stems 132 ofvarious sizes. Each humeral stem 132 may be made such that it can beassembled with tapered shaft 329 of intermediate piece 326.

There have been described and illustrated herein modular prostheticshoulder components. While particular embodiments of the invention havebeen described, it is not intended that the invention be limitedthereto, as it is intended that the invention be as broad in scope asthe art will allow and that the specification be read likewise. Forexample, as described above, the components of the invention may also beadvantageously used in other prosthetic joints such as prosthetic hipjoints.

It will therefore be appreciated by those skilled in the art that yetother modifications could be made to the provided invention withoutdeviating from its spirit and scope as so claimed.

1. A method of implanting a prosthetic device comprising the steps of:inserting a stem of the prosthetic device in an intermedullary canal ofa bone; pivoting a portion of the prosthetic device around anintermediary piece to place the pivoting portion in an optimum position;tightening at least three screws to lock the pivoting portion in theoptimum position; attaching a trial head to the intermediary piece; andproviding openings on the trial head that allow access to the threescrews.
 2. The method of claim 1, further comprising limiting themovement of the pivoting portion of the prosthetic device.
 3. The methodof claim 1, further comprising: removing only the trial head after thepivoting portion has been placed in the optimum position; and installingthe humeral head.
 4. A method of implanting a prosthetic devicecomprising the steps of: inserting a stem of the prosthetic device in anintermedullary canal of a bone; pivoting a portion of the prostheticdevice around an intermediary piece to place the pivoting portion in anoptimum position; tightening at least one screw to fix the pivotingportion in the optimum position; and pouring encapsulant in a cavitynear the screw to lock the pivoting portion in the optimum position. 5.The method of claim 4, further comprising: attaching a trial head to theintermediary piece; and providing at least one opening on the trial headthat allows access to at least one screw.
 6. The method of claim 5,further comprising: removing only the trial head after the pivotingportion has been placed in the optimum position; and installing thehumeral head.
 7. The method of claim 6, further comprising providingopenings in the cavity to allow air to escape when the cavity is filledwith the encapsulant.